Separation of lead 210 from polonium 210 and bismuth 210

ABSTRACT

Separation of lead-210 from polonium-210 by disposing a solution containing at least two of the nuclides wherein one is lead-210 on a platinum substrate, evaporating the solutions and selectively leaching or desorbing the lead-210 with a reagent.

United States Patent 1 Kirby 1 Sept. 11, 1973 [54] SEPARATION OFLEAD-210 FROM 2,894,817 7/1959 Karraker .4 423/2 POLONIUMJ) ANDBISMUTHJ) 3,463,739 8/1969 Schulz et al r 252/30l.l R 3,419,348 12/1968Hardy et a1. .4 423/2 Inventor: Harold y, y OhIO 3,271,320 9/1966 Moore252/301.1 R

[73] Assignee: The United States of America as represented by the UnitedStates Atomic Energy Commission, pninary Emmlller carl QuarfonhWashington DC Asszstant Exammer-F. M. Glttes Attorney-Roland A. Anderson[22] Filed: May 18, 1972 [21] Appl. No.: 254,703

57 ABSTRACT [52] US. Cl. 423/2, 252/30l.1 R [51] Int. Cl G0lg 57/00Separation of lead-210 from polonium-2l0 by dispos- [58] Field of Search423/2, 87, 88; ing a solution containing at least two of the nuclides252/301.l R; 250/106 T wherein one is lead-210 on a platinum substrate,evapcrating the solutions and selectively leaching or desorb- [56].References Cited ing the lead-210 with a reagent.

UNITED STATES PATENTS 2,873,170 2/1959 Hyde et al. 423/2 4 Claims, 1Drawing Figure Pb, Bi and/or SUBSTRATE p0 SOLUTION EVAPORATE REAGENT-RESIDUE DESORBATE CONTAINING 'Pb.

Patented Sept. 11, 1973 3,758,663

EVAPORATE REAGENT RESIDUE EVAPORATE P0 ond/or Bi REAGENT- DESORBADSORBED ON SUBSTRATE DESORBATE CONTAINING Pb.

1 SEPARATION OF LEAD-210 FROM POLONIUM-ZIO AND BISMUTII-ZlO BACKGROUNDOF INVENTION The separation of lead-2 l ("Pb) from its daughtersbismuth-210 ("Bi) and polonium-210 Po) is most desirable to successfuluse of the lead-210 nuclide in physical research programs conducted bygovernment, university, and other research installations. Researchapplications require highly purified lead-210.

Prior methods, such as solvent extraction and anion exchange, used toseparate lead-210 from the aforementioned decay products suffered from anumber of disadvantages or drawbacks. Examples of disadvantages ordrawbacks referred to are a difficulty or inability to derive a highlypurified lead-210 product, and relatively large liquid volumes resultingin dilution of the product.

Thus, for the reasons such as hereinabove noted, it is desirable toprovide an efficient separation process which overcomes the notedproblems and provides a high purity lead-210 product.

SUMMARY OF INVENTION In view of problems as noted above, it is an objectof this invention to provide an improved process for separating lead-210from its decay products polonium-210 and bismuth-210.

It is an object of this invention to provide a lead-210 separationprocess which yields high purity lead-210 product.

It is a further object of this invention to provide a novel lead-210separation process wherein polonium- 210 and bismuth-210 materials reactwith the substrate to facilitate lead-210 desorption.

Various other objects and advantages will appear from the followingdescription of the invention and are particularly pointed outhereinafter in connection with the appended claims. Various changes inprocess flow, materials, etc., as described herein may be made by thoseskilled in the art without departing from the scope and principles ofthis invention as brought out in the appended claims.

The invention comprises a novel method of separating lead-210 from decayproducts by disposing a suitable solution containing said nuclideslead-210 and hismuth-210 and/or polonium-210 on a platinum substrate,evaporating said solution and selectively desorbing essentially lead-210with a reagent.

DESCRIPTION OF DRAWING The drawing illustrates steps in a preferredsequence for operation of this invention.

DETAILED DESCRIPTION As shown in the drawing, a solution from whichlead- 210 is to be separated from polonium-210 and/or bismuth-210 may bedisposed on a platinum substrate. Nuclide containing solutions suitablefor use in disposing the nuclides onto the platinum substrate includeany evaporable liquid or readily volatile acid, such as nitric,hydrochloric or acetic acids, in which the nuclides are soluble.Evaporable liquid or readily volatile nuclide containing solutions suchas from about 1 N to about 6 N hydrochloric acid (I-ICl) and from about1 N to about 6 N nitric acid (HNO have been successfully used. Varioussubstrates, such as tantalum, gold,

iridium, copper and silver may'be used but platinum may provide thehighest and most favorable lead-210 desorption.

The nuclide solutions disposed on the substrate may then be evaporatedso as to leave a dry residue on the substrate. Evaporation may beaccelerated through various means such as heating the substrate,decreasing surface vapor pressure, and other similar methods well knownin the art. Upon completion of evaporation, it may be desired to heatthe substrate as an added assurance of complete evaporation. Thisheating should be maintained below a temperature of about 200C to avoidvolatilization of the polonium and preferably between about 80C andabout 1 10C.

After evaporation of the nuclide solution, a metathesis solution orreagent taken from the group consisting of about 0.01 N to about 1 Nsolution of hydrochloric acid, nitric acid, acetic acid, ammoniumacetate, ammonium chloride, ammonium nitrate and distilled water, may bedisposed on the residue remaining on the substrate after evaporation andit also may be subsequently evaporated. The use of a reagent taken fromthe above group with the residue of the nuclide solution may promoteconversion of the polonium and/or bismuth to a more insoluble form. Thisreagent may then be evaporated and dried using the same heatingprocedure as described hereinabove for the nuclide solution evaporationand drying.

After evaporation of the nuclide solution and, if used, of the reagenttaken from the above listed group, the substrate may be washed in anysuitable manner, such as by flooding, spraying, rinsing or the like,with a suitable reagent or desorbent solution to desorb the lead- 210nuclide. Desorption as herein used refers to the removal of a substrate(such as nuclide lead-210) from an adsorbed state. The washing asdescribed above is in effect a method of separating the essentiallylead-210 nuclide from the absorbed nuclides. Examples of reagents whichmay be used and which have been used with success are distilled water,less than about 1.0 N ammonium acetate, less than about 1 N ammoniumchloride, less than about 0.1 N nitric acid, less than about 0.01 Nhydrofluoric acid, less than about 1 N ammonium nitrate, less than about1 N acetic acid, and preferably, in addition to distilled water, lessthan about 0.3 N ammonium acetate, between about 0.01 N and about 0.3Nammonium chloride, less than about 0.05 N nitric acid, less than about0.01 hydrochloric acid, and less than about 1 N ammonium nitrate. Thesepreferred concentrations may also be used in the previous step in whichone of these reagents is disposed on the residue and then this reagentevaporated in the same manner as the nuclide solution was evaporated.The number of times that the substrate is washed will depend uponindividual methods used, degree of retention of lead-210 after washing,purity required of lead- 210, etc. Two or more washings may bepreferred' Although desorbing or leaching may be conducted at ambienttemperature, it may be preferred to use the temperature range of fromabout C to about 100C.

The method of preparing the surface of the platinum substrate may be afactor in this separation process. For example, platinum substrateswhich may have been covered with hydrochloric acid and subsequentlyheated and then rinsed with distilled water and dried at about C desorbmore polonium-210 and bismuth- 210 than surfaces which may not have hadthis hydrochloric acid surface preparation treatment. This may indicatethat the adsorption of the polonium on the platinum substrate is notmerely a residue adsorption process but involves a chemisorptionprocess, i.e., a process wherein there is both a chemical reaction andadsorption on the substrate surface. Since platinum oxides may bepartially dissolved by the heated hydrochloric acid in the cleaningprocedure, the oxide film may be removed, therefore possibily limitingthe extent to which the polonium-210 could react and become bonded tothe platinum surface. Conversely, ignition of the platinum increases theamount of platinum dioxide (PtO on the substrate surface therebypermitting greater bonding between the polonium-210 and the substrate.Therefore, substrates may be prepared prior to use by heating to a redheat 800C) to enhance the bonding of the Bi and P to the substratesurface.

In Table l, percent adsorption of the various nuclides is noted whileusing various reagents. Substrate Number 15 was pretreated withhydrochloric acid as described above and resulted in a substantialincrease in polonium-210 desorption over substrate sample Number 16which was not acid pretreated.

As noted in Table 1, use of about 0.1 N ammonium chloride (Substrate No.7) was successful in separating lead-210 from the other two nuclides.Reagents used with substrates 1, 2, 3 and 8 were also successfulalthough in a more limited way than the reagent used with substrateNumber 7. Although Table 1 shows examples of high bismuth-210 and insome cases, polonium-210 removal, these are shown merely for the purposeof illustration as to the lower and upper limits. One using thisinvention would draw from the worktable and more efficient examples. Thetemperature reference in Table I refers to the temperature to which theplatinum was heated to dispose the solution on the substrate. Thetemperature at which reagents for desorbing were evaporated may not becritical except to assist in evaporation of the solutions from thesubstrate and to dry the substrate prior to final desorbing.

TABLE 1 Separation of Lead-210 From olonium-210 and Bismuth210 byDesorption From Platinum With Various Reagents Quantity Desorbed Maximum(percent) S bs r e Reagent for Temp.

O- Desorbing "C W *Bi Pb Notes 1 H20 95 0.0 4.4 51.0 (1 2 0.1N CHnCOONH.200 0.08 5.3 72,4 (1 3 0.0lN CHQCOOH 95 0.0 4.3 95.8 (1 4 0.1N CH COOH95 0.1 16.9 98.9 5 0.1N CH CO0NH. 200 0.0 14.0 92.4 6 IN CHJCOOH 95 0.295.7 98.9 7 0.1N NH4CI 200 0.01 Z5 90.9 8 0.1N Nl-hNO 200 0.0 3.4 92.2("l 9 0.0lN HNO: 95 1.4 19.9 99.0 ("1 10 0.1N HNO: 95 22.9 84.5 99.8

ll 3N HNO 95 77.5 99.6 99.9

12 0.000lN HCI 95 0.0 30.9 87.2 (1

13 0.0lN HCI 95 0.0 43.3 99.6 (1

l4 0.1N HCI 95 1.4 96.9 99.8

15 IN HCI 95 39.9 99.8 99.9

16 IN HCl 95 1.1 99.1 99.8 (1

Footnotes:

Deposited from IN HCL solution.

' Deposited from 1N HNO; solution.

5 Preliminary deposition and evaporation of distilled water on nuclidesolution residue before desorbing.

' Platinum was pretreated with 1N HCL before deposition.

...- [4.31:5 .ll. Desorption of Lead-210. Bismuth-210 and Polonium-210From Various Metal Surfaces Quantity Desorbed Water disposed onevaporated residue and evaporated prior to desorption. Substrate ignitedat red heat and cooled before disposing nuclide solution. Maximumtemperature-200C.

' Heated 1 hour at after disposing nuclide solution before desorption.

e Not evaporated to dryness. Solution removed after 1 hour at 25C.

' Data not available.

The tenacity of polonium to a substrate is not limited to platinum but,as is illustrated in Table 11, this tenacity 25 also exists using othersubstrates. These samples shown in Table 11 were disposed from a 1Nhydrochloric acid solution.

As indicated by Table 11, separation on gold surfaces appears to followa pattern more characteristic of physical adsorption. However, becauseof the relatively low softening point of gold, it was feasible toprepare the gold foils prior to deposition of the nuclide containingsolution by igniting the gold foils only briefly. The tantalum andiridium foils were ignited to red heat (-200C) and did adsorb thepolonium more tenaciously than gold but less so than platinum.

Again in Table 11, silver and copper showed a distinct adsorptioneffect, in addition to the usual electrolytic one. Thus the desorptionof bismuth was essentially quantitative when the solution was notevaporated to dryness (Table 11 Number 8) but only half the bismuth- 210could be desorbed after it had been dried and in close contact with thecopper surfaces. Silver appears to react similarly to copper.

It has been found that using the above described procedure comprisingthis invention, lead-210 may be effciently removed from its daughtersbismuth-210 and polonium-210 yielding a high degree of purity lead- 210.Efficiency of lead-210 removed may be about 92 percent or higher.

What is claimed is:

l. The method for separating nuclide lead-210 from nuclides bismuth-210and polonium-210 comprising disposing on a platinum substrate a solutionof evaporable liquid which contains at least one liquid selected fromthe group consisting of distilled water, from about 1 N to about 6 Nhydrochloric'acid, and from about 1 N to about 6 N nitric acid, and thenuclide lead-210 and at least one of the others of said nuclides;evaporating said liquid to dryness; and desorbing nuclide lead- 210 fromsaid substrate by applying thereto a reagent taken from the groupconsisting of distilled water, less than about 0.3 N ammonium acetate,between about 0.01 N and about 0.3 ammonium chloride, less than about0.01 N hydrochloric acid, less than about 0.05 N nitric acid, less thanabout 1 N ammonium nitrate, and less than about 0.2 N acetic acid, saiddesorbing reagent containing said desorbed nuclide lead-210 after and25C before disposing thereon said solution of evaporable liquid.

4. The method of claim ll together with, subsequent to said evaporatingand prior to said desorbing, the preliminary steps of disposing on saidsubstrate said desorbing reagent and evaporating volatile constituentstherefrom.

2. The method of claim 1 together with heating said reagent to atemperature between about 80*C and 100*C during said desorbing.
 3. Themethod of claim 1 together with heating said substrate to a temperaturegreater than about 750*C and then cooling it to temperature betweenabout 22*C and 25*C before disposing thereon said solution of evaporableliquid.
 4. The method of claim 1 together with, subsequent to saidevaporating and prior to said desorbing, the preliminary steps ofdisposing on said substrate said desorbing reagent and evaporatingvolatile constituents therefrom.